Spring 2011 Student ID:_______________________________ Experiment 3: Mixture of Carbonate and Hydroxide and Citric Acid in Soft Drink Quiz #2 (20 points)–April 11, 2011 1. (4 points) Explain the difference between the endpoint and the equivalence point in a titration. The equivalence point is when the moles of titrant are stoichiometrically balanced with those of the analyte. The endpoint is simply the point at which the indicator changes color. The difference between the two is usually very small due to the logarithmic pH scale (if the indicator has been properly chosen). 2. (4 points) What is the purpose of boiling the deionized water in this experiment? (mention in relation to LeChatlier’s principle) Boiling removes dissolved CO 2 . By LeChatlier’s principle, this drives the following reaction to the right and reduces the concentration of carbonic acid. This prevents the extra

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